The present invention relates to a variable nozzle device and in particular to a variable nozzle device for a turbocharger. Also, the invention relates to a parallel configuration of turbochargers and a method for operating the same, a diesel engine boosting system and an engine boosting system.
The International Patent Application PCT/IB03/000042 (published as WO 2004/063535 A1) discloses a parallel configuration of turbochargers (601, 602), wherein both turbines (605, 607) thereof are connected in parallel according to FIG. 4. At low rotational speeds, the second turbocharger is not operated. This configuration needs an external control valve (633) for fully closing the turbine of the second turbocharger at low rotational speeds. At high rotational speeds, the valve must be opened to operate the second turbocharger.
A fully closable nozzle device is known from the Japanese Patent Publication JP-A-2002-038964. The variable nozzle device is constituted by pivotable vanes such that a geometric arrangement of the flow passage is adjustable.
The tips of the pivotable vanes respectively abut against an adjacent vane such that the flow passage through the nozzle is nearly fully closed.
It is the object of the present invention to provide means for fully closing the flow passage to the turbine for a turbocharger having a simplified and reliable structure.